Critical shoulder angle (CSA), lateral acromial angle (LAA), and acromion index (AI) are common radiologic parameters used to distinguish between patients with rotator cuff tears (RCT) and those with an intact rotator cuff. This study aims to assess the predictive power of these parameters in degenerative RCT. This retrospective study included data from 92 patients who were divided into two groups: the RCT group, which included 47 patients with degenerative full-thickness supraspinatus tendon tears, and a control group of 45 subjects without tears. CSA, AI, and LAA measurements from standardized true anteroposterior radiographs were independently derived and analyzed by two orthopedic surgeons. Receiver operating characteristic (ROC) analyses were performed to determine the cutoff values. No significant differences were found between patients in the RCT and control groups in age (p = 0.079), gender (p = 0.804), or injury side (p = 0.552). Excellent inter-observer reliability was seen for CSA, LAA, and AI values. Mean CSA (38.1°) and AI (0.72) values were significantly larger in the RCT group than in the control group (34.56° and 0.67°, respectively, p < 0.001) with no significant difference between groups for LAA (RCT, 77.99° vs. control, 79.82°; p = 0.056). ROC analysis yielded an area under the curve (AUC) of 0.815 for CSA with a cutoff value of 37.95°, and CSA was found to be the strongest predictor of the presence of a RCT, followed by AI with an AUC of 0.783 and a cutoff value of 0.705. We conclude that CSA and AI may be useful predictive factors for degenerative RCT in the Turkish population

A cadaver study using six pairs of lower limbs was conducted to investigate the accuracy of computer navigation and standard instrumentation for the placement of the Birmingham Hip Resurfacing femoral component. The aim was to place all the femoral components with a stem-shaft angle of 135°.

The mean stem-shaft angle obtained in the standard instrumentation group was 127.7° (120° to 132°), compared with 133.3° (131° to 139°) in the computer navigation group (p = 0.03). The scatter obtained with computer-assisted navigation was approximately half that found using the conventional jig.

Computer navigation was more accurate and more consistent in its placement of the femoral component than standard instrumentation. We suggest that image-free computer-assisted navigation may have an application in aligning the femoral component during hip resurfacing.